The objectives of this proposal are to biochemically and physically characterize mechanisms by which specific hormonal effects are mediated within gonadotropin-responsive cells, as well as to biochemically characterize specific hormone receptors and other subcellular components. Mechanisms responsible for gonadotropin receptor biogenesis and down regulation will be examined by a combination of radiolabeling and immunocytochemical techniques or by alternative purification techniques. Methods for introducing solubilized receptor into liposomes will be systematically investigated in an effort to maintain or reinstill specific gonadotropin binding of the solubilized receptors. Specific solubilized FSH and LH receptors will be isolated by affinity chromatography and their biochemical nature examined. In addition, antibody to highly purified solubilized gonadotropin receptors will be used to study intracellular mechanisms modulating receptor turnover. The intracellular fate of the subunits of cyclic AMP dependent protein kinases will be examined, including their possible interaction with nuclei isolated from gonadotropin-responsive cells.